Portland District > Missions > Flood Risk Management

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A place in history

The 1964 Christmas Flood and the 1996 floods devastated many areas of Oregon and Washington, but these floods would have been much worse if the Corps hadn't been able to store water behind their dams as it poured into the uncontrolled rivers and tributaries. The Corps’ existing and under-construction reservoir storage projects in the Willamette River Basin during the 1964 flood prevented over $510 million in damages in 1965 dollars. The 2014 value of that flood management effort is almost $3.9 billion. Since their completion, this system of dams has cumulatively prevented more than $20 billion in flood damages, including more than $2 billion during the flood of 1996.

Flood Risk Management

Green Peter Dam The foremost goal of the Corps’ Flood Risk Management mission is to save lives and reduce property damage from flooding. While every year brings the possibility of a large flood, risks have decreased since the days when the Willamette and the Columbia rivers overflowed their banks almost yearly, laying watery waste to whole communities.

While no one action or agency can eliminate flood risks, the Corps:

Improves public understanding of federal, state and local agencies’ roles
Assists communities in developing responses to flood risks and hazards. These can include non-structural measures, earthen levees, concrete and steel floodwalls, gate closures and drainage and floodplain improvements.
Encourages better decision-making by governments, individuals, the private sector and non-governmental organizations and provides technical information
Counters or corrects rumors to improve public understanding of risks from flooding.

Rain and snow: it all goes downhill

Photo of two kids filling sandbags on a sunny day.

Flooding typically occurs when runoff from rain and snow-melt flows over riverbanks and onto floodplains. Heavy or continuous rain west of the Cascade mountain range generates the greatest amount of runoff from November through March. Snow-melt runoff east of the Cascades is typically the cause of flooding from May through July. The potential for damage from these floods increases in the densely populated and highly developed areas in or near the Columbia River’s floodplain, such as Salem and Portland in Oregon and Vancouver, Washington. The Corps’ reservoirs capture vast quantities of water and wetlands absorb floodwaters to take the peak off many floods. Watch this video to learn more about how dams work to manage water.

Through collaborative action with other federal, state and local agencies, however, risks to public safety from floods and the damage they cause are reduced significantly. Many agencies, including the Corps, assist communities with non-structural measures that help reduce floods and their consequences, such as establishing flood response plans and considering land development plans to reduce flood risks and hazards.

The actions of property owners, residents and businesses can reduce flood risks even more and improve response and recovery actions should a flood occur.

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Explaining flood risk

Simply put, flood risk is the probability that an area will flood combined with the negative consequences, such as property damage or the loss of life. In more detail, this risk is the combination of several factors: the probability that the amount of runoff will be large enough to cause flooding, the ability to reduce human risks and damage from a flood, and the actual consequences should flooding occur. Reducing any one of these factors can reduce flood risk. Residual flood risk may remain after all efforts to reduce the risk are complete; it is the exposure to the risk and potential loss remaining after other known risks have been countered, factored in or eliminated.

An updated approach to flood risk management

The government once used the term “flood control” for its efforts to protect people and property from flooding, but no one agency or set of actions can control flooding. There are limits to both the ability to predict floods and the level of protection that the Corps, other agencies or human measures can provide.

The Corps focuses its policies, programs and expertise on reducing overall flood risk. This includes the appropriate use of structures such as dams, levees and floodwalls. It also promotes alternatives such as land acquisition, flood-proofing and landowners’ consideration of the purchase of flood insurance. Such alternatives reduce the risks to public safety, reduce long-term economic damages and improve the natural environment.

The Corps’ national Flood Risk Management Program is moving away from the heavily engineered solutions seen 50 years ago. It embraces a more comprehensive flood risk reduction strategy that emphasizes the importance of property owners, residents, communities and government understanding their roles and responsibilities in reducing overall flood risks before actual flooding occurs. For information, including an overview of flood risk management grants, visit Frequently Asked Questions.

Shared responsibility for flood risk management

Flood risk management in the United States is a shared responsibility that includes property owners and government agencies alike. Many federal, state and local government agencies participate through a complex set of programs and authorities. Nationally, programs within the Corps, the Federal Emergency Management Agency and other federal agencies assist states and communities in reducing flood damages and promoting sound flood risk management practices. These agencies also provide valuable technical information to communities and individuals to improve their understanding of their risk. For this approach to be effective, individuals must weigh the costs and advantages of using this information to take action and further reduce risk, whether it is for a community, a household or a business.

State and local governments determine how land in floodplains is used and enforce related requirements. These floodplain management choices can impact the effectiveness of federal programs and efforts to mitigate flood risk. A key requirement for success is to ensure that as public and government leaders make flood risk management decisions, they integrate environmental, social, and economic factors and consider all available tools to improve public safety.

Explore flood risk management from your perspective

For more information on the databases, programs and initiatives, and models and tools available to for the water resources community in the U.S. and internationally, please see the Federal Support Toolbox for Integrated Water Resources Management.

Community action

As an individual or business owner, you should understand your flood risk, take action to reduce that risk, and know what to do if you are impacted by a flood. For more information about what you should know and what you can do, visit http://www.nwp.usace.army.mil/Missions/Emergency/Preparedness.aspx.

Visit http://www.oregon.gov/LCD/HAZ/pages/propowndev.aspx to learn:

how to read a flood hazard map
how to obtain a flood hazard map
about floodplain insurance
about permits for work in the floodplain
find determinations that property is in or outside the floodplain
about avoiding and limiting flood damages, and
get more technical guidance on various floodplain management issues.

Federal programs to reduce risk, develop solutions

Congress authorized several programs under which the Corps assists state and local governments in assessing their flood risk and developing solutions. Each program has its unique eligibility requirements and authorities. This is a partial list.

Floodplain Management Services Program. Upon request, and without charge, the Corps will furnish to states, tribes, counties, and cities the floodplain information and technical assistance needed in planning for prudent use of land subject to flooding from streams, lakes and oceans.
Planning Assistance to States Program. Upon request, the Corps will support states in their preparation of plans for the development, use and conservation of water and related land resources located within the boundaries of the state.
The Inspection of Completed Works Program is used to determine if flood risk management projects are properly operated and maintained.
The National Nonstructural Flood Proofing Committee works within the Corps, providing strategies for reducing flood risk without using structures such as levees or floodwalls or in combination with these structural solutions for the most efficient and effective flood risk reduction.
Under Public Law 84-99, the Corps has the ability to provide rehabilitation assistance for flood risk management projects damaged during flood events. Through the voluntary Rehabilitation Program, the Corps will assist in repairing levee systems and other flood risk management projects after a flood event, if the project meets the required eligibility criteria.

The Federal Emergency Management Agency administers the National Flood Insurance Program, which provides access to flood insurance for individuals and businesses.

Through the NFIP and programs such as the Community Rating System (CRS), communities can learn about and take actions to reduce flood risk (and lower their flood insurance premiums) in their communities.

The Environmental Protection Agency Office of Water provides tools and guidance for managing stormwater, which a community may incorporate as part of its comprehensive flood risk management approach.

Silver Jackets: partners in risk reduction

The Corps participates and promotes awareness of the Oregon Silver Jackets program, which is a collaborative state-led interagency team which continuously works together to reduce flood risk in Oregon. Visit http://www.nfrmp.us/state/about.cfm.